Charmed Baryon Decays and their asymmetries

Charmed Baryon Decays and their asymmetries

Charmed Baryon Decays
and their asymmetries
B.G. Cheon
(Hanyang Univ., Korea)
For the Belle collaboration
Charm2012, 14/May, Hawaii
1
Contents
• Introduction
• Spectroscopic strong/EM decays
– Review of c, c-excitation families.
• Hadronic weak decays
– Updated results from Belle/BaBar
– Status of doubly charmed baryon search
• Decay asymmetry
• Summary
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Why charmed baryons?
• Charmed baryon strong/EM decays provide lots of excited states.
–
–
–
–
More orbital excitation states (Q+qq) than meson(Q+q).
Less phase space for decays and narrower states.
Established 17 charmed baryons up to date. (refer PDG).
Fruitful experimental results on excited states, but a few unpromoted states.
• Charmed baryon weak decays are suitable to study decay dynamics.
– Still poor measurements in weak decays of c+, c+, c0 , Wc0
• Theoretical predictions can be tested and motivated to new approaches.
Ground state (L=0) baryon listings
3
Strong/EM decays
4
c-excitation family
•
•
Good consistent among Belle, BaBar and CLEO measurements.
Isospin singlets : c(2880)+, c(2940)+
– Due to no isospin partners in D+p @ Babar
– Belle measured spin-parity of c(2880)+
•
c(2940)+ : 5MeV below D*p threshold
– Exotics? hep-ph/0606015
– Conventional baryon? PRD75,094017; JPG34, 961; PRD75, 094017 (2007)
•
c(2765) : should be studied in more depth.
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c (2765)  c+ p+ p- ?
PRL 98, 012001 (2007) : BaBar
PRL 98, 262001 (2007) : Belle
c(2880)
Measured JP
c(2880)
c(2940)
c(2940)
D0 p
c(2765) ?
c(2455)0p+
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Spin-parity
(2880)+ Scp c+p+p-
PRL 98, 262001 (2007) : Belle
Sc(2455)
•
JP [c(2880)+]
J = 5/2 favored
•
Sc(2520)
Sc(2455)
•
Heavy Quark Symmetry
–
–
Sc(2800)0
threshold
enhancement
B- c+pp-
J = 3/2
R = 1.4 : 5/2R ~ 0.3 : 5/2+
PRD 78, 112003 (2008) : BaBar
JP [Sc(2445)0]
J = 1/2
•
J = 1/2 favored
Sc(2455)0
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Sc(2455), Sc(2520), c(2595), c(2625)
Sc(2455) Sc(2520)
•
•
•
c+(Jp = 1/2+)
– only weak decay
Sc (2455) (Jp = 1/2+),
Sc (2520) (Jp = 3/2+)
– L=0 orbital excitations
– Isospin triplets : 0, +, ++
– Strong decay to c p
c (2595) (Jp = 1/2-),
c (2625) (Jp = 3/2-)
– L=1 orbital excitations
– Isospin singlets : +
– Strong decay to c p p
– c (2595) S-wave res.
– c (2625) D-wave res.
– Non-res. P-wave
PRD 84, 012003 (2011)
Sc++
c(2625)
Sc
+
c(2595)
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Sc(2455), Sc(2520), c(2595), c(2625)
PRD 84, 012003 (2011)
•
•
•
•
Consistent with previous exp. results
Considerable improvement in c(2595), c(2625)
Pion coupling constant (h2) measured.
Discrepancy in c(2595) mass with previous results
–
–
Due to proper treatment of kinematical thresh. effect
Refer to PRD 67, 074033 (2003).
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c-excitation family
•
•
•
Good consistent between BaBar and Belle measurements.
Isospin doublets : c(2980), c(3077)
c(2930)+, c(3055)+, c(3123)+ : unpromoted states
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c (2930)  c+K- ?
PRL 97, 202003 (2006) : Belle
PRD 77, 031101 (2008) : BaBar
B- c+c-K-
B- c+c-K-
c +c -
c +K -
c +c -
c(2930) ?
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c (3055,3132)  c+ K p- ?
PRL 97, 162001 (2006) : Belle
PRD 77, 012002 (2008) : BaBar
c +K -p +
c(3055) ?
c+Ks0p+
c(3123) ?
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Weak decays
14
Updated results from Babar/Belle
15
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Doubly charmed baryons
cc+  c+ K- p+ + p D+ K-
cc++  c+ K- p+ p+
PRL 89, 112001 (2002) : SELEX
NPB proc. 115, 33 (2003) : FOCUS
PLB 628, 18 (2005) : SELEX
PRD 74, 011103 (2006) : BaBar
{CCq}
preliminary
•
SELEX reported the observation of cc+
–
–
–
cc+  c+ K- p+
•
No confirmed by FOCUS/Belle/BaBar
–
–
•
measured m(cc+) = 3518.7 (1.8) MeV/c2
Theory : m(cc+) = ~ 3610 MeV/c2
t (measured) < t (theory)
BELLE : < 1.5 x 10-4 @ 90% CL
BaBar : < 2.4 x 10-4 @ 95% CL
LHCb under MC study in active.
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Decay Asymmetry
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Decay asymmetry
Predicted asymmetry parameter (a)
•
•
•
•
Parity violation occurs in charm
baryon decays due to existence
of two orbital angular mom.
decay amplitudes of opposite
parity.
The experimental observable is
an asymmetry in the angular
decay distribution due to
interference between the two
amplitudes.
Many theoretical predictions
have been made so that one
can rule out some of them by
measuring a.
However, just few measurements
available with large error so far.
Rather recent measurement(2006) by FOCUS:
Under detail study @ Belle
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c
0

+
p
decay asymmetry
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CPV search
• CPV in baryonic decays has never been measured so far.
• Expected ACP in the Standard Model is quite small.
• Only FOCUS and CLEO made in charmed baryon decays.
PLB 634, 165 (2000)
PRL 94, 191801 (1994)
• Better stat. & syst. sensitivities can be achieved in Belle.
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CPV search at Belle
• Search mode : c+   p+
• Basic strategy is blind analysis with MC sample at initial stage.
– Kinematic reconstruction
– Cut optimization
• Procedure of ACP measurement is well established.
– Measure signal yields in cosq bins.
– Extract ACP from measured a and a-bar
• Expected sensitivity
MC study
– da = ~ 0.5% (stat.)
– dACP = ~7% (stat.)
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Summary
• Most of recent contributions done by BaBar and Belle.
• Good shape in measurement of strong/EM decays.
– Need confirmation of unpromoted states.
• Still poor stage in measurement of weak decays.
– Hope to see doubly charmed baryons in a few years.
– Under study of decay asymmetry and CPV.
– Need absolute BF measurements, model-indep. BF(cpKp).
• Waiting for remarkable results from running/upcoming exp.
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감사합니다!
Thank you
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